But Western Officials See Slow Progress in Talks, and Iran Resists Key Demand on Enrichment

MUNICH—A final deal to curb Iran’s nuclear program remains elusive after the latest talks, with Tehran refusing to move on a central demand to significantly curtail uranium enrichment, Western officials said Sunday.

Iran’s lead negotiator, Foreign Minister Javad Zarif, got a boost Sunday from Supreme Leader Ayatollah Ali Khamenei, who signaled he could back a compromise accord but would oppose a deal he saw as hurting Iran’s interests. Mr. Khamenei is widely seen as the final arbiter of Iran’s security policies.